The Papanicolaou Cancer Research Institute (PCRI) maintains the Dunning R3327 tumor which is a hormone response, slow growing adenocarcinoma. This tumor is transplanted into Copenhagen x Fischer Fl males for use in prostatic adenocarcinoma research projects. The PCRI maintains breeding colonies of Copenhagen rats and Fischer 344 rats to produce the hybrids. Tumor-bearing rats, uninnoculated controls and frozen tumor tissue are supplied to investigators. A quality control program insures that the biological characteristics of the origin tumor are maintained. A joint project is underway with several other investigators to fully define the tumor model system.